活性炭基固体酸催化合成己酸乙酯的研究

以白酒酒糟制备的活性炭作为载体,通过磺化反应制备具有高酸值的活性炭基固体酸催化剂,确定最佳制备条件为:活性炭目数120目,固液比1∶5,磺化时间24h。用制备的固体酸催化剂催化合成己酸乙酯,分别考察了固体酸催化剂的添加量、酸醇比、酯化时间和酯化温度对酯化反应的影响,得出反应的最佳条件是:固体酸添加量是己酸质量的4%,酸醇比为1∶10,酯化时间为12h,酯化温度为98℃。此时己酸乙酯酯化率达71%。     

二氧化硅-硫酸氢钾固体酸催化制备生物柴油

采用溶胶-凝胶法制备KHSO4.SiO2固体酸催化剂,将其应用于催化油酸与甲醇制备生物柴油的酯化反应中,考察了催化剂焙烧温度、KHSO4负载量、甲醇与油酸物质的量比、催化剂用量、反应时间及催化剂使用次数对生物柴油转化率的影响。结果表明,固体酸催化剂KHSO4.SiO2在油酸与甲醇的酯化反应中具有很高的催化活性,最佳反应条件:催化剂焙烧温度为200℃,KHSO4负载量为20%,甲醇与油酸物质的量比为12∶1,催化剂用量占油酸质量的10%,反应时间5 h,生物柴油转化率可达95.58%。固体酸催化剂KHSO4.SiO2可重复使用4次,催化活性良好。     

微波辅助绿豆碳基固体酸催化剂活性研究

为了考察微波辐射对自制固体酸催化剂催化活性的影响,作者以绿豆为原料,采用碳化-磺化法制备了一种新型碳基固体酸催化剂,于实验室自制微波反应器中催化油酸和甲醇的酯化反应。对油酸甲酯化反应过程中的微波功率、反应温度、反应时间、催化剂用量、醇油摩尔比等条件进行了单因素分析,并对醇油摩尔比、反应时间、催化剂用量对油酸甲酯化的转化率的影响进行了正交优化,得到最佳工艺为:微波功率400 W、反应温度65℃、醇油摩尔比11∶1、反应时间30 min、催化剂用量为5%,在此工艺条件下油酸甲酯化的转化率为93.97%。     

SO2-4/水淬渣固体酸催化脂肪酸制备生物柴油

以硫酸处理炼锌水淬渣所得的活性物质为载体,采用浸渍法制备了固体超强酸。将该固体酸用于甲醇和油酸的酯化反应,通过考察反应条件对油酸转化率的影响来反映固体酸在油酸和甲醇酯化反应中的催化活性。结果表明：当固体酸用量为油酸质量的18%、甲醇与油酸的摩尔比为15∶1、反应温度为120℃、反应时间为8 h时,油酸转化率可达90.35%;固体酸催化剂重复使用3次后,油酸转化率仍在70%以上,但随着重复利用次数增加,其催化活性有所下降。     

SO_4~(2-)/水淬渣固体酸催化脂肪酸制备生物柴油

以硫酸处理炼锌水淬渣所得的活性物质为载体,采用浸渍法制备了固体超强酸。将该固体酸用于甲醇和油酸的酯化反应,通过考察反应条件对油酸转化率的影响来反映固体酸在油酸和甲醇酯化反应中的催化活性。结果表明:当固体酸用量为油酸质量的18%、甲醇与油酸的摩尔比为15∶1、反应温度为120℃、反应时间为8 h时,油酸转化率可达90.35%;固体酸催化剂重复使用3次后,油酸转化率仍在70%以上,但随着重复利用次数增加,其催化活性有所下降。     

活性炭基固体酸催化合成酒用脂肪酸乙酯的研究

以白酒酒糟为原料,通过浓硫酸磺化制备了活性炭基固体酸催化剂,并催化合成乙酸乙酯、乳酸乙酯、己酸乙酯和丁酸乙酯4种酒用脂肪酸乙酯。结果表明,乙酸乙酯最佳反应条件为活性炭基固体酸催化剂添加量3%,酸醇物质的量比1∶5,酯化时间4 h,酯化温度80 ℃,酯化率达86%;乳酸乙酯最佳反应条件为催化剂添加量4%,酸醇物质的量比1∶8,酯化时间10 h,酯化温度95 ℃,酯化率达76%;己酸乙酯最佳反应条件为催化剂添加量4%,酸醇物质的量比1∶10,酯化时间12 h,酯化温度98 ℃,酯化率达68%;丁酸乙酯最佳反应条件为催化剂添加量4%,酸醇物质的量比1∶9,酯化时间8 h,酯化温度90 ℃,酯化率达73%。活性炭基固体酸催化剂可以重复使用6次。     

生物炭基固体酸催化剂制备及其催化油酸酯化性能的研究

以去除半纤维素的玉米芯为原料，通过高温炭化、浓硫酸磺化制备了生物炭基固体酸催化剂，用于油酸酯化制备生物柴油，并对催化剂进行了表征。考察了炭化温度、炭化时间、磺化温度、磺化时间等制备条件对催化剂的影响，探究了反应温度、反应时间、醇油摩尔比、催化剂质量分数对油酸酯化反应的影响。结果表明，适宜的催化剂制备条件为300 ℃炭化3 h、25 ℃磺化4 h，在此条件下制备的生物炭基固体酸酸量为1.67 mmol/L；适宜的反应条件为反应温度65 ℃，反应时间5 h，甲醇与油酸的摩尔比12：1，催化剂质量分数4%，在此条件下，油酸转化率为98%。催化剂在使用4次后，催化剂活性下降至63%，经过重新磺化，油酸转化率可恢复至94%。     

马铃薯粉炭基固体酸催化制备生物柴油研究

将马铃薯粉作为炭化材料,再用浓硫酸进行磺化,制备了高活性高稳定性的炭基固体酸催化剂,采用SEM、BET、FT-IR和XRD对其进行表征,并应用于催化油酸与甲醇的酯化反应中。结果表明:该催化剂为随机排列的芳香族碳片组成的无定型碳结构,呈现块状、疏松、边缘粗糙的形貌;结构中含有多环芳烃,且磺酸基已成功负载;催化剂孔结构主要以介孔为主,能为反应物和活性位点的接触提供通道。当酯化温度为65℃、酯化时间为2. 5 h、醇油摩尔比为10∶1、催化剂用量(占油酸的质量)为5%时,油酸转化率达到95. 68%。再生后的催化剂在重复利用5次后,油酸转化率仍可达89. 56%。     

硅藻土固载硅钨酸盐催化油酸甲酯化研究

采用一锅法制备了硅藻土固载铁掺杂的硅钨酸(FeSiW/硅藻土)固体酸催化剂,使用傅里叶红外光谱(FT-IR)及扫描电子显微镜(SEM)对催化剂的结构及形貌进行了分析,结果发现铁掺杂的硅钨酸较好的分散在硅藻土的表面。将其应用于油酸与甲醇为反应物的生物柴油制备体系,催化活性研究发现在催化剂用量3%(以油酸质量为基准)、油酸与甲醇摩尔比为1∶8、反应温度70℃、反应时间4 h的条件下,酯化反应转化率为72.5%,且催化剂重复使用6次后,转化率仍高于70%。此外,FeSiW/硅藻土催化剂还适用于催化各种长链羧酸的酯化反应。     

新型海藻酸铬复合物的制备及其催化油酸甲酯化合成生物柴油

以海藻酸钠与氯化铬为原料制备出一种价格低廉的新型海藻酸铬复合物,通过XRD、FTIR、SEM对制备的复合物结构进行表征,并将其应用于催化油酸与甲醇酯化反应制备生物柴油。系统考察了各因素对油酸转化率的影响,并研究了该催化剂在各种酯化反应中的应用。结果表明:廉价、易制备的海藻酸铬复合物固体酸表现出较高的催化活性,在催化剂用量3%(相对于油酸的质量)、油酸与甲醇摩尔比1∶10、反应温度70℃、反应时间3 h条件下,油酸转化率达92.2%;催化剂经重复使用5次,油酸的转化率仍高于60%;此外,该催化剂能适用各种长链羧酸与甲醇的酯化反应,表明该催化剂有望用于工业上高酸值原料降酸制备生物柴油。     

Reliable identification of grapevine rootstock varieties using RAPD PCR on woody samples

Since grapevine ( Vitis spp .) rootstock material is being traded increasingly as disbudded woody material a lack of distinctive morphological features on such material necessitates an alternative and reliable means of identification. Methods described here were developed for rapid and efficient extraction of DNA from woody samples rich in phenolic compounds and polysaccharides, and for subsequent identification of varieties by RAPD PCR. Using these methods, and with the application of only one selected RAPD primer, we were able to differentiate sixteen rootstock varieties, including the seven varieties most commonly used in Germany. Problems commonly encountered with reproducibility of RAPD patterns were avoided by choosing primers with a dinucleotide sequence and a high G/C content that allowed a rather high annealing temperature of 45°C. Methods described here should also be useful for other horticultural crops, especially those with woody tissues rich in phenolic compounds and polysaccharides.     

An internet compendium of analytical methods and spectroscopic information for monomers and additives used in food packaging plastics

An internet website (http://cpf.jrc.it/smt/) has been produced as a means of dissemination of methods of analysis and supporting spectroscopic information on monomers and additives used for food contact materials (principally packaging). The site which is aimed primarily at assisting food control laboratories in the European Union contains analytical information on monomers, starting substances and additives used in the manufacture of plastics materials. A searchable index is provided giving PM and CAS numbers for each of 255 substances. For each substance a data sheet gives regulatory information, chemical structures, physico-chemical information and background information on the use of the substance in particular plastics, and the food packaging applications. For monomers and starting substances (155 compounds) the infra-red and mass spectra are provided, and for additives (100 compounds); additionally proton NMR are available for about 50% of the entries. Where analytical methods have been developed for determining these substances as residual amounts in plastics or as trace amounts in food simulants these methods are also on the website. All information is provided in portable document file (PDF) format which means that high quality copies can be readily printed, using freely available Adobe Acrobat Reader software. The website will in future be maintained and up-dated by the European Commission's Joint Research Centre (JRC) as new substances are authorized for use by the European Commission (DG-ENTR formerly DGIII). Where analytical laboratories (food control or other) require reference substances these can be obtained free-ofcharge from a reference collection housed at the JRC and maintained in conjunction with this website compendium.     

Aroma characterization of various apricot varieties using headspace–solid phase microextraction combined with gas chromatography–mass spectrometry and gas chromatography–olfactometry

The characterization of the aromatic profile of several apricot cultivars with molecular tracers in order to obtain objective data concerning the aromatic quality of this fruit was undertaken using headspace–solid phase microextraction (HS–SPME). Six apricot cultivars were selected according to their organoleptic characteristics: Iranien, Orangered, Goldrich, Hargrand, Rouge du Roussillon and A4025. The aromatic intensity of these varieties measured by HS–SPME–Olfactometry were defined and classified according to the presence and the intensity of grassy, fruity and apricot like notes. In the six varieties, 23 common volatile compounds were identified by HS–SPME–GC–MS. Finally, 10 compounds, ethyl acetate, hexyl acetate, limonene, β-cyclocitral, γ-decalactone, 6-methyl-5-hepten-2-one, linalool, β-ionone, menthone and (E)-hexen-2-al were recognized by HS–SPME–GC–O as responsible of the aromatic notes involved in apricot aroma and considered as molecular tracers of apricot aromatic quality which could be utilized to discriminate apricot varieties.     

Textural Properties of Cold-set Gels Induced from Heat-denatured Whey Protein Isolates

A 9% whey protein (WP) isolate solution at pH 7.0 was heat-denatured at 80°C for 30 min. Size-exclusion HPLC showed that native WP formed soluble aggregates after heat-treatment. Additions of CaCl2 (10–40 mM), NaCl (50–400 mM) or glucono-delta-lactone (GDL, 0.4–2.0%, w/v) or hydrolysis by a protease from Bacillus licheniformis caused gelation of the denatured solution at 45°C. Textural parameters, hardness, adhesiveness, and cohesiveness of the gels so formed changed markedly with concentration of added salts or pH by added GDL. Maximum gel hardness occurred at 200 mM NaCl or pH 4.7. Increasing CaCl2 concentration continuously increased gel hardness. Generally, GDL-induced gels were harder than salt-induced gels, and much harder than the protease-induced gel.     

Tests of potential functional barriers for laminated multilayer food packages. Part I: Low molecular weight permeants

The advent of the functional barrier concept in food packaging has brought with it a requirement for fast tests of permeation through potential barrier materials. In such tests it would be convenient for both foodstuffs and materials below the functional barrier (sub-barrier materials) to be represented by standard simulants. By means of inverse gas chromatography, liquid paraffin spiked with appropriate permeants was considered as a potential simulant of sub-barrier materials based on polypropylene (PP) or similar polyolefins. Experiments were performed to characterize the kinetics of the permeation of low molecular weight model permeants (octene, toluene and isopropanol) from liquid paraffin, through a surrogate potential functional barrier (25 μm-thick oriented PP) into the food simulants olive oil and 3% (w/v) acetic acid. These permeation results were interpreted in terms of three permeation kinetic models regarding the solubility of a particular model permeant in the post-barrier medium (i.e. the food simulant). The results obtained justify the development and evaluation of liquid sub-barrier simulants that would allow flexible yet rigorous testing of new laminated multilayer packaging materials.     

Occurrence of bisphenol-F-diglycidyl ether (BFDGE) in fish canned in oil

The levels of bisphenol-F-diglycidyl ether (BFDGE) were quantified as part of a European survey on the migration of residues of epoxy resins into oil from canned fish. The contents of BFDGE in cans, lids and fish collected from all 15 Member States of the European Union and Switzerland were analysed in 382 samples. Cans and lids were separately extracted with acetonitrile. The extraction from fish was carried out with hexane followed by re-extraction with acetonitrile. The analysis was performed by reverse phase HPL C with fluorescence detection. BFDGE could be detected in 12% of the fish, 24% of the cans and 18% of the lids. Only 3% of the fish contained BFDGE in concentrations considerably above 1mg/kg. In addition to the presented data, a comparison was made with the levels of BADGE (bisphenol-A-diglycidyl ether)analysed in the same products in the context of a previous study.     

Contribution of European research to risk analysis

The European Commission's, Quality of Life Research Programme, Key Action 1—Health, Food & Nutrition is mission-oriented and aims, amongst other things, at providing a healthy, safe and high-quality food supply leading to reinforced consumer confidence in the safety of European food. Its objectives also include the enhancing of the competitiveness of the European food supply. Key Action 1 is currently supporting a number of different types of European collaborative projects in the area of risk analysis. The objectives of these projects range from the development and validation of prevention strategies including the reduction of consumers risks; development and validation of new modelling approaches; harmonization of risk assessment principles, methodologies, and terminology; standardization of methods and systems used for the safety evaluation of transgenic food; providing of tools for the evaluation of human viral contamination of shellfish and quality control; new methodologies for assessing the potential of unintended effects of genetically modified (genetically modified) foods; development of a risk assessment model for Cryptosporidium parvum related to the food and water industries; to the development of a communication platform for genetically modified organism, producers, retailers, regulatory authorities and consumer groups to improve safety assessment procedures, risk management strategies and risk communication; development and validation of new methods for safety testing of transgenic food; evaluation of the safety and efficacy of iron supplementation in pregnant women; evaluation of the potential cancer-preventing activity of pro- and pre-biotic ('synbiotic') combinations in human volunteers. An overview of these projects is presented here.     

低温带皮菜籽粕微粉的不同粒级部分的功能特性

为研究低温带皮菜籽粕微粉的不同粒级部分的功能特性,以经低温脱脂的带皮菜籽粕为原料,经微粉碎后筛分成212~425μm、150~212μm和106~150μm的3个不同粒级的微粉样品,检测这些样品的吸水性、吸油性、乳化性和乳化稳定性、蛋白质体外消化率。结果表明:1 3个不同粒级的微粉样品之间的粗纤维含量存在显著差异,表明三者的结构组成成分有一定差异。23个微粉样品的乳化活性和乳化稳定性随粒度级别的减小而显著增加(P0.01)。33个微粉样品的蛋白质体外消化率随粒度级别的减小而显著增加(P0.01)。4不同粒级带皮菜籽粕微粉样品的吸水性与吸油性受其结构组成物质不同和粒度的双重影响,与粒度的相关性不明显。     

Microbiology of food taints

Fresh and processed foods are often spoilt by the presence of undesirable flavours and odours caused by microbial action. The aim of this paper is to review the current knowledge of microbiologically induced taints that occur in a wide range of foodstuffs, including meats, poultry, fish, crustaceans, milk, dairy products, fruits, vegetables, cereals and cereal products. Examples have been chosen where the compounds responsible for the taint have been identified and sufficient data obtained to demonstrate the involvement of microorganisms. However, in some cases the full identity of the causative organism may not have been elucidated. The types of microorganisms covered by this review include bacteria, fungi, yeasts, actinomycetes and cyanobacteria. Although cyanobacteria do not in general infect foods, their presence in aqueous systems and water supplies can lead to off-flavours in aquatic organisms and processed foodstuffs. Several examples of each of these processes are discussed. Wherever possible, the likely biosynthetic pathway used by the microorganism to produce the offending compound in a foodstuff is indicated.